In general, a communication method between vehicles in a tunnel analyzes and adapt to radio channel characteristics per tunnel so as to prevent signal distortion and information loss according to the radio channel characteristics of the tunnel. That is, it is necessary to install a relay station inside the tunnel. It is common to model a communication channel in each section of the tunnel before the relay station is installed, and to install the relay station after the analysis is completed.
Using conventional radio communication, it is hard to handle disasters or accidents in terms of a tunnel system. When a frequency broadcast by a corresponding vehicular system is not monitored continuously, the accident in the tunnel is not recognized. Hence, a vehicle driver needs to monitor the corresponding frequency all the time. The conventional vehicular communication focuses on the accident information transfer function after the accident takes place, rather than the accident prevention function.
A conventional wireless system for the tunnel analyzes a tunnel environment, for example, channel conditions and then installs the relay station in accordance with the tunnel environment. Disadvantageously, when the tunnel is extended or altered, the installed relay station is unusable. In this case, it is burdensome to analyze the modified tunnel environment and to install a new relay station. In this regard, communication system and method for more efficiently sending information to the vehicle in the tunnel are demanded.